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Darwin Correspondence Project

From Robert Russell   27 February 1868

Pilmuir, Leven, Fifeshire

27 Feby 1868

Charles Darwin Esq,


Noticing your request in Agl. Gazette of 15th. inst, as to the proportion of sexes in domestic animals I willingly contribute a mite.1

I have a sheep farm in the west Highlands consisting of Black faced stock. I had noticed that I have always a larger number of ewe lambs than of Tup. After seeing your note I wrote a neighbour of mine there of long and extensive experience. I have just had his answer which confirms my own experience. He writes that the ewes predominate over the Tup lambs on an average to the extent of 12 per cent. This he says may be held as true for the Black faced sheep over the Highlands.2 The pasturage is poor, consisting of heath and coarse mountain grasses. The stocks go on the hills all winter and are often pinched for food during snow storms. Twin lambs are in small numbers and 3 at a birth is very rare. I have often asked the question of myself “Does scanty fare tend to produce more Ewe Lambs?

Among stocks of pure Leicester sheep which are all high fed the sexes may be assumed as nearly equal.—even where from 23 rd. to 34 of the Ewes produce 2 at a birth and 110 th. three

As regards the other domestic animals I could not give you any reliable information.

I take this opportunity of sending you a paper of mine on certain conditions that favour the growth and predominance of plants. You will observe that at page 22 I came pretty close upon your “law of competition” or “Natural Selection.” before your work appeared.3 Baron Liebig4 adopted and acknowledge the views I put forth here. I discussed the conditions that favour the predominance of trees in my work on “North America”.5

I assure you that I derived great pleasure from the work “Origin of Species”.

with much esteem | I am | Your most obd Sert. | Robert Russell

P.S. In this part of the country I have been informed that among Partridges the Cock-birds are considerably more than double those of the hen-birds in number.


CD annotations

2.2 larger] underl red crayon
2.2 ewe] underl red crayon
2.2 Tup] underl red crayon
2.5 12 per cent.] underl red crayon
3.1 stocks of pure Leicester] underl red crayon
3.1 Among … three 3.3] ‘—Leicester sexes equal.—’ added ink
3.2 assumed as nearly equal] underl red crayon
3.2 23 rd.... Ewes] underl red crayon
4.1 As … esteem 7.1] crossed red crayon
8.1 P.S.... number. 8.2] scored red crayon
End of letter: ‘Black faced ewe lambs preponderate 12 per cent’ ink
End of postscript: ‘Robert Russell’ pencil


See letter to Gardeners’ Chronicle, 11 February [1868]. The full name of the journal was Gardeners’ Chronicle and Agricultural Gazette.
CD gave details on the proportion of the sexes in sheep, including blackfaced sheep bred in Scotland, in Descent 1: 304. DAR 85: B57 contains a list of sex ratios in blackfaced sheep, and includes an entry for 124 males and 112 females bred by Russell in 1869.
Russell published several papers on agriculture (Royal Society catalogue of scientific papers); the paper referred to may have been an offprint of R. Russell 1859, a two-part article on the climate and soil conditions favourable to various cereal plants (see R. Russell 1859, pp. 481–2). It has not been found in the Darwin Pamphlet Collection–CUL.
Russell visited the United States, Canada, and Cuba in 1854 and published a book on the climate of North America (R. Russell 1857; for the discussion of trees, see pp. 112–13, 260–1).


Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

Royal Society catalogue of scientific papers: Catalogue of scientific papers (1800–1900). Compiled and published by the Royal Society of London. 19 vols. and index (3 vols.). London: Royal Society of London. Cambridge: Cambridge University Press. 1867–1925.

Russell, Robert. 1857. North America: its agriculture and climate: containing observations on the agriculture and climate of Canada, the United States, and the island of Cuba. Edinburgh: Adam and Charles Black.

Russell, Robert. 1859. On the influence of climate on cultivation. Journal of the Royal Agricultural Society of England 20: 158–74, 481–97.


A reply to CD’s inquiry in Gardeners’ Chronicle [Collected papers 2: 135]. The proportion of females to males in lambs of highland black-faced sheep.

Sends paper on conditions that favour predominance of plants.

Letter details

Letter no.
Robert Russell
Charles Robert Darwin
Sent from
Leven, Fife
Source of text
DAR 85: B21; DAR 86: C16
Physical description
ALS 3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 5945,” accessed on 1 October 2023,

Also published in The Correspondence of Charles Darwin, vol. 16